Alternators with permanent magnets have been known for many years. For various reasons they have not, however, been widely used in automotive installations. Such alternators would have significant advantages in automotive applications. They have a small number of moving parts and are therefore dependable. They can be very compact and also electrically efficient. This latter characteristic is important as modern motor vehicles are making ever increasing demands on their electrical supply; so much so that it is becoming increasingly common for motor vehicles to be fitted with, for example, 12 volt, 50 amp alternators which usually require a twin pulley, twin v-belt drive with concomitant robustness of construction, bearings etc as well as increased fuel consumption.
It is not clear why permanent magnet-type alternators are not widely used in the market place in automotive applications. One reason may be that no economically viable regulator has hitherto been produced which is capable of regulating the output voltage thereof over wide variations in speed and power demands. This would seem to be borne out by the fact that such alternators used in motor cycles have only crude regulators which comprise essentially simple inductances. This is very deleterious for the batteries to which they are connected.